The present invention relates to a combine harvester.
After a crop has been cut from a field by a combine harvester, it is processed by a threshing mechanism, beaters, shakers and a sieve unit to separate the grain from the remainder, which is made up of crop residue and chaff. The type of crop residue will depend on the nature of the crop being harvested, and the term is used herein to include such larger items as straw, stalks, corn cobs and other thick plant parts. The chaff on the other hand is much finer and includes such items as husks.
It is well known, for example from WO01/01754, for the crop residue and the chaff to be discharged separately from the rear of the combine harvester and to be processed differently, the crop residue being discharged from shakers that are positioned above and to the rear of the sieving unit from which the chaff is discharged.
As explained in the introduction of WO01/01754, modern combine harvesters are becoming ever larger with cutting tables which are significantly wider than the width of the harvester proper. For various reasons, amongst them the risk of fire resulting from the heat generated by such large combine harvesters, it is important to be able to disperse the crop residue and the chaff as far sideways and backwards as possible from the combine harvester.
A chaff discharging device provided at the discharge end of the sieving unit conventionally comprises a blower that can disperse the chaff sideways and rearwards over a large area. To disperse the crop residue, on the other hand, a chopper is provided behind the chaff discharging device to receive and process the material discharged from the shakers. The chopper cuts the crop residue into small pieces which are then dispersed to the side and rear of the harvester. The area over which the crop residue and the chaff are dispersed is preferably as wide as the cutting table so that they can later both be ploughed back uniformly into the soil.
It is sometimes preferred not to cut the crop residue in the chopper but instead to lay strings or swaths behind the combine harvester for later collection. This could be done for example with straw so that the straw may later be massed into bales or it may be done with corn cobs to avoid damaging the cutting blades of the chopper.
It is therefore known to provide a deflector at the inlet of the chopper that can be set to one of two positions. In the first position, the inlet of the chopper is uncovered and the crop residue flows into the mouth of the chopper so that it may be chopped and dispersed as earlier described. In the second position, the deflector covers the mouth of the chopper so that instead of entering into the chopper, the crop residue falls to the ground in the gap between the chaff discharging device and the chopper forming a swath behind the combine harvester.
It has also been proposed in U.S. Pat. No. 6,547,169, assigned to CNH America LLC and titled “Crop Residue Spreader for an Agricultural Combine”, to disperse the chaff using a spreader rather than a blower, the spreader being designed to be capable of spreading the crop residue as well as the chaff. With the deflector positioned to prevent the crop residue from entering the chopper, the spreader can be set in either of two positions. In the first position, it allows the crop residue to fall to the ground to form a swath while in the second position it lies in the path of the crop residue so that the chaff and the uncut crop residue are together dispersed to the side and rear of the combine harvester.
In a combine harvester where the gap between the chopper and the chaff discharging device is restricted, it is known for that gap to become blocked with crop residue because of the rate at which the bulky crop residue is discharged through it. This problem is aggravated if the chaff discharging device is brought nearer to the chopper, as occurs in the harvester described in the above mentioned U.S. patent, and when the cutting table is made wider, as is the trend in modern combine harvesters.